D-bifunctional protein deficiency

What causes D-bifunctional protein (DBP) deficiency?

DBP deficiency is caused by mutations in the HSD17B4 gene. This gene codes for a special type of protein, called D-bifunctional protein, which is an enzyme (helps biochemical reactions take place). The D-bifunctional protein is found in structures within our cells called peroxisomes, which contain several different enzymes that break down different substances. The D-bifunctional protein is involved in breaking down products of fats in our diet called fatty acids. The protein has two separate parts with different enzyme activity, called hydratase and dehydrogenase domains. These domains help carry out the second and third steps of a metabolic process called the peroxisomal fatty acid beta-oxidation pathway. This pathway breaks down fatty acid molecules so they can be transported out of the peroxisomes for reuse by the cell.

Mutations in the HSD17B4 gene that cause D-bifunctional protein deficiency can affect one or both of the protein's functions. Although this does not seem to affect the severity of the symptoms of the disorder, the condition may be grouped into three types based on which enzyme(s) is/are deficient:

  • Type 1 - deficiency of both enzymes
  • Type 2 - deficiency of hydratase
  • Type 3 - deficiency of dehydrogenase

Impairment of one or both of the protein's functions prevents the ability of the protein from breaking down fatty acids properly, resulting in a buildup of fatty acids in the body. It is not clear how the fatty acid buildup leads to the symptoms of this disorder.

Last updated on 05-01-20

How is D-bifunctional protein (DBP) deficiency diagnosed?

DBP deficiency can be diagnosed based on lab results showing increased levels of the following: (1) very long-chain fatty acids; (2) α-methyl- branched fatty acids such as pristanic acid and its precursor phytanic acid; and (3) Bile acid intermediates dihydroxycholestanoic acid (DHCA) and trihydroxycholestanoic acid (THCA). Genetic testing may be useful to confirm the diagnosis.

Last updated on 05-01-20

Name: United Leukodystrophy Foundation (ULF) 224 North Second Street Suite 2
DeKalb, IL, 60115 , United States
Phone: 815-748-3211 Toll Free: 800-728-5483 Fax : 815-748-0844 Email: office@ulf.org Url: http://www.ulf.org/
Name: Global Foundation for Peroxisomal Disorders 5147 South Harvard Avenue Suite 181
Tulsa, OK, 74135, United States
Phone: 347-470-4373 Fax : 918-516-0227 Email: contactus@thegfpd.org Url: http://www.thegfpd.org
Name: Alex The Leukodystrophy Charity Alex TLC 45 Peckham High Street
London, SE15 5EB, United Kingdom
Phone: 020 7701 4388 Email: info@alextlc.org Url: https://www.alextlc.org

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